The Relative 'Importance' of Life-History Stages to Population Growth: Prospective and Retrospective Analyses

1997 ◽  
Author(s):  
Carol Horvitz ◽  
Douglas W. Schemske ◽  
Hal Caswell
Keyword(s):  
Life History ◽  
Population Growth ◽  
Relative Importance ◽  
Life History Stages

Demography of Xenosaurus platyceps (Squamata: Xenosauridae): a comparison between tropical and temperate populations

2008 ◽  
Vol 29 (2) ◽  
pp. 245-256 ◽  
Author(s):  
Carissa Jones ◽  
Isaac Rojas-González ◽  
Julio Lemos-Espinal ◽  
Jaime Zúñiga-Vega
Keyword(s):  
Life History ◽  
Population Growth ◽  
Adult Mortality ◽  
Life History Strategies ◽  
Relative Importance ◽  
Theoretical Frameworks ◽  
Population Growth Rates ◽  
Relative Contribution ◽  
Two Populations ◽  
Average Fitness

Abstract There appears to be variation in life-history strategies even between populations of the same species. For ectothermic organisms such as lizards, it has been predicted that demographic and life-history traits should differ consistently between temperate and tropical populations. This study compares the demographic strategies of a temperate and a tropical population of the lizard Xenosaurus platyceps. Population growth rates in both types of environments indicated populations in numerical equilibrium. Of the two populations, we found that the temperate population experiences lower adult mortality. The relative importance (estimated as the relative contribution to population growth rate) of permanence and of the adult/reproductive size classes is higher in the temperate population. In contrast, the relative importance for average fitness of fecundity and growth is higher in the tropical population. These results are consistent with the theoretical frameworks about life-historical differences among tropical and temperate lizard populations.

The influence of multi-stage predation on population growth and the distribution of the pond-breeding salamander, Ambystoma jeffersonianum

2006 ◽  
Vol 84 (3) ◽  
pp. 449-458 ◽  
Author(s):  
M J Rubbo ◽  
K Shea ◽  
J M Kiesecker
Keyword(s):  
Life History ◽  
Population Growth ◽  
Field Experiments ◽  
Predation Pressure ◽  
Field Surveys ◽  
Life History Stages ◽  
Ambystoma Jeffersonianum ◽  
Multi Stage ◽  
Fundamental Goal ◽  
Distributional Patterns

Understanding the drivers of distributional patterns is a fundamental goal of ecology. For many organisms, distributions are determined by the habitats in which breeding occurs. Therefore, determining the factors that limit post-ovipositional success in specific habitats is critical to deciphering the factors that shape distributions. Using field surveys and laboratory, mesocosm, and field experiments, we conducted a study of the breeding effort of the salamander Ambystoma jeffersonianum (Green, 1827) in sites of varying predation pressure and the susceptibility of its embryos and larvae to predators. We then used these data to parameterize a matrix model examining the effects of predation on population growth. We found that A. jeffersonianum egg masses were less abundant in ponds with higher predation pressure. Moreover, A. jeffersonianum performance was negatively affected by both embryonic and larval predators. The results of the model suggest that only predation acting upon multiple life-history stages can limit population growth for A. jeffersonianum. These data provide support for the hypothesis that multi-stage predation can shape breeding distributions by imposing strong selective costs in specific environments. Furthermore, these data highlight the importance of conducting multi-stage studies and utilizing multiple ecological methodologies when addressing the factors that limit the distribution and abundance of organisms.

Life history and environmental influences on population dynamics in sockeye salmon

2014 ◽  
Vol 71 (8) ◽  
pp. 1198-1208 ◽  
Author(s):  
Douglas C. Braun ◽  
John D. Reynolds
Keyword(s):  
Population Dynamics ◽  
Life History ◽  
Population Growth ◽  
Growth Rates ◽  
Environmental Conditions ◽  
Sockeye Salmon ◽  
Life History Traits ◽  
Relative Importance ◽  
Population Growth Rates ◽  
Habitat Variables

Understanding linkages among life history traits, the environment, and population dynamics is a central goal in ecology. We compared 15 populations of sockeye salmon (Oncorhynchus nerka) to test general hypotheses for the relative importance of life history traits and environmental conditions in explaining variation in population dynamics. We used life history traits and habitat variables as covariates in mixed-effect Ricker models to evaluate the support for correlates of maximum population growth rates, density dependence, and variability in dynamics among populations. We found dramatic differences in the dynamics of populations that spawn in a small geographical area. These differences among populations were related to variation in habitats but not life history traits. Populations that spawned in deep water had higher and less variable population growth rates, and populations inhabiting streams with larger gravels experienced stronger negative density dependence. These results demonstrate, in these populations, the relative importance of environmental conditions and life histories in explaining population dynamics, which is rarely possible for multiple populations of the same species. Furthermore, they suggest that local habitat variables are important for the assessment of population status, especially when multiple populations with different dynamics are managed as aggregates.

Relative importance of reproductive life-history paths in one population of the lizard Sceloporus grammicus

2012 ◽  
Vol 33 (3-4) ◽  
pp. 401-413
Author(s):  
J. Jaime Zúñiga-Vega ◽  
Claudia Molina-Zuluaga ◽  
Oswaldo Hernández-Gallegos ◽  
Norma L. Manríquez-Morán ◽  
Felipe Rodríguez-Romero ◽  
...  
Keyword(s):  
Life History ◽  
Population Growth ◽  
Growth Rates ◽  
Fast Growth ◽  
Relative Importance ◽  
Population Growth Rates ◽  
Relative Contribution ◽  
Reproductive Life ◽  
Sceloporus Grammicus ◽  
Reproductive Life History

Life cycles of living organisms are composed of distinct sub-cycles that represent alternative life-history paths with differential impact on fitness. We identified three reproductive life-history paths (referred here as loops) in the life cycle of one population of the viviparous lizard Sceloporus grammicus. We evaluated the relative importance of each one of these reproductive paths for the population fitness of these lizards during a 5-year period. The first path corresponded to early reproduction and included survival to maturity and early fecundity. The second path was late reproduction loop and included survival to larger adult sizes with the corresponding fecundity rate. The third was composed of those individuals skipping the small adult stage within a single year, reaching larger sizes early in life with their corresponding larger litters (fast growth loop). To examine the potential effects of environmental factors on the relative contribution of these alternative life-history paths to fitness, we estimated stage-specific survival and growth as functions of annual temperature and rainfall. Using these estimates of vital rates we constructed annual population projection matrices. Then, using demographic elasticities and loop analysis, we calculated the relative contribution of each of the three reproductive paths to the population growth rates. Our results showed that the early reproduction loop is the path with the greatest relative contribution to the population growth rate in most years. However, increases in environmental temperature resulted in higher population growth rates and in greater contribution of the fast growth path to the overall fitness of these lizards.

scholarly journals The movement ecology of seagrasses

2014 ◽  
Vol 281 (1795) ◽  
pp. 20140878 ◽  
Author(s):  
Kathryn McMahon ◽  
Kor-jent van Dijk ◽  
Leonardo Ruiz-Montoya ◽  
Gary A. Kendrick ◽  
Siegfried L. Krauss ◽  
...  
Keyword(s):  
Life History ◽  
Clonal Growth ◽  
Movement Ecology ◽  
Future Research ◽  
The Novel ◽  
Long Distance ◽  
Spatial And Temporal Scales ◽  
Life History Stages ◽  
Research Areas ◽  
Time Movement

A movement ecology framework is applied to enhance our understanding of the causes, mechanisms and consequences of movement in seagrasses: marine, clonal, flowering plants. Four life-history stages of seagrasses can move: pollen, sexual propagules, vegetative fragments and the spread of individuals through clonal growth. Movement occurs on the water surface, in the water column, on or in the sediment, via animal vectors and through spreading clones. A capacity for long-distance dispersal and demographic connectivity over multiple timeframes is the novel feature of the movement ecology of seagrasses with significant evolutionary and ecological consequences. The space–time movement footprint of different life-history stages varies. For example, the distance moved by reproductive propagules and vegetative expansion via clonal growth is similar, but the timescales range exponentially, from hours to months or centuries to millennia, respectively. Consequently, environmental factors and key traits that interact to influence movement also operate on vastly different spatial and temporal scales. Six key future research areas have been identified.

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